Drill charger diagnostics

No LEDs, etc to tell you what is going on?

The LEDs (charging, fully-charged) are both off. There is no voltage at the charger's output, which is why I opened it up to find out if I could where the fault is.

Daniele

I would not expect an output from the transformer unless there is a load on it. And the load would be detected by the components on the PCB.

Right. Must be pretty old if it has an actual transformer, rather than a SMPS. But a short etc after the transformer could have caused it to burn out.

Difficult to know without seeing it how easy it would be to replace the transformer. You could trawl through Ebay or CPS etc for spares - but you'd likely pay less for a complete used charger than a new transformer, even if you can find an exact one. And if it's old the battery likely well past its best.

If old iron cored transformer then it may have an embedded thermal fuse in the primary winding. It's usually possible (if being careful) to cut back the insulation and bypass said fuse - purely for testing purposes of course.

You really don't need to go any further. Even if the charger is faulty and you can fix it, that won't help. The batteries are bound to be knackered.

I'm not full of joy at the moment, you may have noticed, the reason being that I went for a scan before having an operation and they told me that they found something else. So, that's two operations - one major and one a bit less so. I'm not feeling optimistic about myself, so I'm buggered if I'm going to feel optimistic about your bleeding drill.

Dave Plowman (News) has brought this to us :

SMPSU's have transformers too.

WTF?

The transformer is generally the least likely item to fail, but it looks like it has. Measure the resistance of the secondary winding to be sure (with power disconnected)

NT

I'm very sorry to hear it, and I would very happily give up any hope for my drill in exchange for some cause for optimism for you. So I wish you the very best of luck.

Daniele

That surprises me. I would have expected to see 18V or whatever on the output side leads, *unless* something in the PCB were shorting them (and in which case, I would expect the fuse to have blown).

Daniele

Thanks. I very much hope that I have a better chance than your drill. :)

That was pretty close to what I said, actually.

Going to peg it then?

I can't agree. Thermal fuses age, plus if the regulation circuit is faulty that can apply a larger than designed load on the transformer its going to go pop.

As an example, I have in front of me a charger with a transformer. Strangely the 3A plug fuse is o/c, and when replaced there is no output from the transformer. The PCB has some beefy diodes, but the PCB below these is blackened from heat.

I bought a new (old stock) charger and measured the transformer output to find 30Vac. This charger is for Bosch 7.2V to 24V battery packs.

Mortality for the main op is around 2%, so the chances are rather high that you'll have to put up with me a bit longer. None of this involves a computerectomy.

Adam you're being horrible! And what do you mean, a transformer won't have any voltage on the output unless it has a load?

Bill

Adam's going to peg it, too. It's only the timescale that's in doubt.

Unloaded transformers give a much higher output voltage than their rating, only falling into the normal range when loaded.

SteveW